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<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a>
<FONT color="green">003</FONT>     * contributor license agreements.  See the NOTICE file distributed with<a name="line.3"></a>
<FONT color="green">004</FONT>     * this work for additional information regarding copyright ownership.<a name="line.4"></a>
<FONT color="green">005</FONT>     * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a>
<FONT color="green">006</FONT>     * (the "License"); you may not use this file except in compliance with<a name="line.6"></a>
<FONT color="green">007</FONT>     * the License.  You may obtain a copy of the License at<a name="line.7"></a>
<FONT color="green">008</FONT>     *<a name="line.8"></a>
<FONT color="green">009</FONT>     *      http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a>
<FONT color="green">010</FONT>     *<a name="line.10"></a>
<FONT color="green">011</FONT>     * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a>
<FONT color="green">012</FONT>     * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a>
<FONT color="green">013</FONT>     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a>
<FONT color="green">014</FONT>     * See the License for the specific language governing permissions and<a name="line.14"></a>
<FONT color="green">015</FONT>     * limitations under the License.<a name="line.15"></a>
<FONT color="green">016</FONT>     */<a name="line.16"></a>
<FONT color="green">017</FONT>    package org.apache.commons.math.random;<a name="line.17"></a>
<FONT color="green">018</FONT>    <a name="line.18"></a>
<FONT color="green">019</FONT>    import org.apache.commons.math.MathRuntimeException;<a name="line.19"></a>
<FONT color="green">020</FONT>    <a name="line.20"></a>
<FONT color="green">021</FONT>    /**<a name="line.21"></a>
<FONT color="green">022</FONT>     * Abstract class implementing the {@link  RandomGenerator} interface.<a name="line.22"></a>
<FONT color="green">023</FONT>     * Default implementations for all methods other than {@link #nextDouble()} and<a name="line.23"></a>
<FONT color="green">024</FONT>     * {@link #setSeed(long)} are provided. <a name="line.24"></a>
<FONT color="green">025</FONT>     * &lt;p&gt;<a name="line.25"></a>
<FONT color="green">026</FONT>     * All data generation methods are based on &lt;code&gt;nextDouble().&lt;/code&gt;<a name="line.26"></a>
<FONT color="green">027</FONT>     * Concrete implementations &lt;strong&gt;must&lt;/strong&gt; override<a name="line.27"></a>
<FONT color="green">028</FONT>     * this method and &lt;strong&gt;should&lt;/strong&gt; provide better / more<a name="line.28"></a>
<FONT color="green">029</FONT>     * performant implementations of the other methods if the underlying PRNG<a name="line.29"></a>
<FONT color="green">030</FONT>     * supplies them.&lt;/p&gt;<a name="line.30"></a>
<FONT color="green">031</FONT>     *<a name="line.31"></a>
<FONT color="green">032</FONT>     * @since 1.1<a name="line.32"></a>
<FONT color="green">033</FONT>     * @version $Revision: 796543 $ $Date: 2009-07-21 17:32:38 -0400 (Tue, 21 Jul 2009) $<a name="line.33"></a>
<FONT color="green">034</FONT>     */<a name="line.34"></a>
<FONT color="green">035</FONT>    public abstract class AbstractRandomGenerator implements RandomGenerator {<a name="line.35"></a>
<FONT color="green">036</FONT>        <a name="line.36"></a>
<FONT color="green">037</FONT>        /** <a name="line.37"></a>
<FONT color="green">038</FONT>         * Cached random normal value.  The default implementation for <a name="line.38"></a>
<FONT color="green">039</FONT>         * {@link #nextGaussian} generates pairs of values and this field caches the<a name="line.39"></a>
<FONT color="green">040</FONT>         * second value so that the full algorithm is not executed for every<a name="line.40"></a>
<FONT color="green">041</FONT>         * activation.  The value &lt;code&gt;Double.NaN&lt;/code&gt; signals that there is<a name="line.41"></a>
<FONT color="green">042</FONT>         * no cached value.  Use {@link #clear} to clear the cached value.<a name="line.42"></a>
<FONT color="green">043</FONT>         */<a name="line.43"></a>
<FONT color="green">044</FONT>        private double cachedNormalDeviate = Double.NaN;<a name="line.44"></a>
<FONT color="green">045</FONT>        <a name="line.45"></a>
<FONT color="green">046</FONT>        /**<a name="line.46"></a>
<FONT color="green">047</FONT>         * Construct a RandomGenerator.<a name="line.47"></a>
<FONT color="green">048</FONT>         */<a name="line.48"></a>
<FONT color="green">049</FONT>        public AbstractRandomGenerator() {<a name="line.49"></a>
<FONT color="green">050</FONT>            super();<a name="line.50"></a>
<FONT color="green">051</FONT>            <a name="line.51"></a>
<FONT color="green">052</FONT>        }<a name="line.52"></a>
<FONT color="green">053</FONT>        <a name="line.53"></a>
<FONT color="green">054</FONT>        /**<a name="line.54"></a>
<FONT color="green">055</FONT>         * Clears the cache used by the default implementation of <a name="line.55"></a>
<FONT color="green">056</FONT>         * {@link #nextGaussian}. Implemementations that do not override the<a name="line.56"></a>
<FONT color="green">057</FONT>         * default implementation of &lt;code&gt;nextGaussian&lt;/code&gt; should call this<a name="line.57"></a>
<FONT color="green">058</FONT>         * method in the implementation of {@link #setSeed(long)}<a name="line.58"></a>
<FONT color="green">059</FONT>         */<a name="line.59"></a>
<FONT color="green">060</FONT>        public void clear() {<a name="line.60"></a>
<FONT color="green">061</FONT>            cachedNormalDeviate = Double.NaN;<a name="line.61"></a>
<FONT color="green">062</FONT>        }<a name="line.62"></a>
<FONT color="green">063</FONT>    <a name="line.63"></a>
<FONT color="green">064</FONT>        /** {@inheritDoc} */<a name="line.64"></a>
<FONT color="green">065</FONT>        public void setSeed(int seed) {<a name="line.65"></a>
<FONT color="green">066</FONT>            setSeed((long) seed);<a name="line.66"></a>
<FONT color="green">067</FONT>        }<a name="line.67"></a>
<FONT color="green">068</FONT>    <a name="line.68"></a>
<FONT color="green">069</FONT>        /** {@inheritDoc} */<a name="line.69"></a>
<FONT color="green">070</FONT>        public void setSeed(int[] seed) {<a name="line.70"></a>
<FONT color="green">071</FONT>            // the following number is the largest prime that fits in 32 bits (it is 2^32 - 5)<a name="line.71"></a>
<FONT color="green">072</FONT>            final long prime = 4294967291l;<a name="line.72"></a>
<FONT color="green">073</FONT>    <a name="line.73"></a>
<FONT color="green">074</FONT>            long combined = 0l;<a name="line.74"></a>
<FONT color="green">075</FONT>            for (int s : seed) {<a name="line.75"></a>
<FONT color="green">076</FONT>                combined = combined * prime + s;<a name="line.76"></a>
<FONT color="green">077</FONT>            }<a name="line.77"></a>
<FONT color="green">078</FONT>            setSeed(combined);<a name="line.78"></a>
<FONT color="green">079</FONT>        }<a name="line.79"></a>
<FONT color="green">080</FONT>    <a name="line.80"></a>
<FONT color="green">081</FONT>        /**<a name="line.81"></a>
<FONT color="green">082</FONT>         * Sets the seed of the underyling random number generator using a <a name="line.82"></a>
<FONT color="green">083</FONT>         * &lt;code&gt;long&lt;/code&gt; seed.  Sequences of values generated starting with the<a name="line.83"></a>
<FONT color="green">084</FONT>         * same seeds should be identical.<a name="line.84"></a>
<FONT color="green">085</FONT>         * &lt;p&gt;<a name="line.85"></a>
<FONT color="green">086</FONT>         * Implementations that do not override the default implementation of <a name="line.86"></a>
<FONT color="green">087</FONT>         * &lt;code&gt;nextGaussian&lt;/code&gt; should include a call to {@link #clear} in the<a name="line.87"></a>
<FONT color="green">088</FONT>         * implementation of this method.&lt;/p&gt;<a name="line.88"></a>
<FONT color="green">089</FONT>         *<a name="line.89"></a>
<FONT color="green">090</FONT>         * @param seed the seed value<a name="line.90"></a>
<FONT color="green">091</FONT>         */<a name="line.91"></a>
<FONT color="green">092</FONT>        public abstract void setSeed(long seed);  <a name="line.92"></a>
<FONT color="green">093</FONT>    <a name="line.93"></a>
<FONT color="green">094</FONT>        /**<a name="line.94"></a>
<FONT color="green">095</FONT>         * Generates random bytes and places them into a user-supplied <a name="line.95"></a>
<FONT color="green">096</FONT>         * byte array.  The number of random bytes produced is equal to <a name="line.96"></a>
<FONT color="green">097</FONT>         * the length of the byte array.<a name="line.97"></a>
<FONT color="green">098</FONT>         * &lt;p&gt;<a name="line.98"></a>
<FONT color="green">099</FONT>         * The default implementation fills the array with bytes extracted from<a name="line.99"></a>
<FONT color="green">100</FONT>         * random integers generated using {@link #nextInt}.&lt;/p&gt;<a name="line.100"></a>
<FONT color="green">101</FONT>         * <a name="line.101"></a>
<FONT color="green">102</FONT>         * @param bytes the non-null byte array in which to put the <a name="line.102"></a>
<FONT color="green">103</FONT>         * random bytes<a name="line.103"></a>
<FONT color="green">104</FONT>         */<a name="line.104"></a>
<FONT color="green">105</FONT>        public void nextBytes(byte[] bytes) {<a name="line.105"></a>
<FONT color="green">106</FONT>            int bytesOut = 0;<a name="line.106"></a>
<FONT color="green">107</FONT>            while (bytesOut &lt; bytes.length) {<a name="line.107"></a>
<FONT color="green">108</FONT>              int randInt = nextInt();<a name="line.108"></a>
<FONT color="green">109</FONT>              for (int i = 0; i &lt; 3; i++) {<a name="line.109"></a>
<FONT color="green">110</FONT>                  if ( i &gt; 0) {<a name="line.110"></a>
<FONT color="green">111</FONT>                      randInt = randInt &gt;&gt; 8;<a name="line.111"></a>
<FONT color="green">112</FONT>                  }<a name="line.112"></a>
<FONT color="green">113</FONT>                  bytes[bytesOut++] = (byte) randInt;<a name="line.113"></a>
<FONT color="green">114</FONT>                  if (bytesOut == bytes.length) {<a name="line.114"></a>
<FONT color="green">115</FONT>                      return;<a name="line.115"></a>
<FONT color="green">116</FONT>                  }<a name="line.116"></a>
<FONT color="green">117</FONT>              }<a name="line.117"></a>
<FONT color="green">118</FONT>            }<a name="line.118"></a>
<FONT color="green">119</FONT>        }<a name="line.119"></a>
<FONT color="green">120</FONT>    <a name="line.120"></a>
<FONT color="green">121</FONT>         /**<a name="line.121"></a>
<FONT color="green">122</FONT>         * Returns the next pseudorandom, uniformly distributed &lt;code&gt;int&lt;/code&gt;<a name="line.122"></a>
<FONT color="green">123</FONT>         * value from this random number generator's sequence.  <a name="line.123"></a>
<FONT color="green">124</FONT>         * All 2&lt;font size="-1"&gt;&lt;sup&gt;32&lt;/sup&gt;&lt;/font&gt; possible &lt;tt&gt;int&lt;/tt&gt; values<a name="line.124"></a>
<FONT color="green">125</FONT>         * should be produced with  (approximately) equal probability. <a name="line.125"></a>
<FONT color="green">126</FONT>         * &lt;p&gt;<a name="line.126"></a>
<FONT color="green">127</FONT>         * The default implementation provided here returns <a name="line.127"></a>
<FONT color="green">128</FONT>         * &lt;pre&gt;<a name="line.128"></a>
<FONT color="green">129</FONT>         * &lt;code&gt;(int) (nextDouble() * Integer.MAX_VALUE)&lt;/code&gt;<a name="line.129"></a>
<FONT color="green">130</FONT>         * &lt;/pre&gt;&lt;/p&gt;<a name="line.130"></a>
<FONT color="green">131</FONT>         *<a name="line.131"></a>
<FONT color="green">132</FONT>         * @return the next pseudorandom, uniformly distributed &lt;code&gt;int&lt;/code&gt;<a name="line.132"></a>
<FONT color="green">133</FONT>         *  value from this random number generator's sequence<a name="line.133"></a>
<FONT color="green">134</FONT>         */<a name="line.134"></a>
<FONT color="green">135</FONT>        public int nextInt() {<a name="line.135"></a>
<FONT color="green">136</FONT>            return (int) (nextDouble() * Integer.MAX_VALUE);<a name="line.136"></a>
<FONT color="green">137</FONT>        }<a name="line.137"></a>
<FONT color="green">138</FONT>    <a name="line.138"></a>
<FONT color="green">139</FONT>        /**<a name="line.139"></a>
<FONT color="green">140</FONT>         * Returns a pseudorandom, uniformly distributed &lt;tt&gt;int&lt;/tt&gt; value<a name="line.140"></a>
<FONT color="green">141</FONT>         * between 0 (inclusive) and the specified value (exclusive), drawn from<a name="line.141"></a>
<FONT color="green">142</FONT>         * this random number generator's sequence. <a name="line.142"></a>
<FONT color="green">143</FONT>         * &lt;p&gt;  <a name="line.143"></a>
<FONT color="green">144</FONT>         * The default implementation returns <a name="line.144"></a>
<FONT color="green">145</FONT>         * &lt;pre&gt;<a name="line.145"></a>
<FONT color="green">146</FONT>         * &lt;code&gt;(int) (nextDouble() * n&lt;/code&gt;<a name="line.146"></a>
<FONT color="green">147</FONT>         * &lt;/pre&gt;&lt;/p&gt;<a name="line.147"></a>
<FONT color="green">148</FONT>         *<a name="line.148"></a>
<FONT color="green">149</FONT>         * @param n the bound on the random number to be returned.  Must be<a name="line.149"></a>
<FONT color="green">150</FONT>         * positive.<a name="line.150"></a>
<FONT color="green">151</FONT>         * @return  a pseudorandom, uniformly distributed &lt;tt&gt;int&lt;/tt&gt;<a name="line.151"></a>
<FONT color="green">152</FONT>         * value between 0 (inclusive) and n (exclusive).<a name="line.152"></a>
<FONT color="green">153</FONT>         * @throws IllegalArgumentException if n is not positive.<a name="line.153"></a>
<FONT color="green">154</FONT>         */<a name="line.154"></a>
<FONT color="green">155</FONT>        public int nextInt(int n) {<a name="line.155"></a>
<FONT color="green">156</FONT>            if (n &lt;= 0 ) {<a name="line.156"></a>
<FONT color="green">157</FONT>                throw MathRuntimeException.createIllegalArgumentException(<a name="line.157"></a>
<FONT color="green">158</FONT>                      "upper bound must be positive ({0})", n);<a name="line.158"></a>
<FONT color="green">159</FONT>            }<a name="line.159"></a>
<FONT color="green">160</FONT>            int result = (int) (nextDouble() * n);<a name="line.160"></a>
<FONT color="green">161</FONT>            return result &lt; n ? result : n - 1;<a name="line.161"></a>
<FONT color="green">162</FONT>        }<a name="line.162"></a>
<FONT color="green">163</FONT>    <a name="line.163"></a>
<FONT color="green">164</FONT>         /**<a name="line.164"></a>
<FONT color="green">165</FONT>         * Returns the next pseudorandom, uniformly distributed &lt;code&gt;long&lt;/code&gt;<a name="line.165"></a>
<FONT color="green">166</FONT>         * value from this random number generator's sequence.  All <a name="line.166"></a>
<FONT color="green">167</FONT>         * 2&lt;font size="-1"&gt;&lt;sup&gt;64&lt;/sup&gt;&lt;/font&gt; possible &lt;tt&gt;long&lt;/tt&gt; values <a name="line.167"></a>
<FONT color="green">168</FONT>         * should be produced with (approximately) equal probability. <a name="line.168"></a>
<FONT color="green">169</FONT>         * &lt;p&gt;  <a name="line.169"></a>
<FONT color="green">170</FONT>         * The default implementation returns <a name="line.170"></a>
<FONT color="green">171</FONT>         * &lt;pre&gt;<a name="line.171"></a>
<FONT color="green">172</FONT>         * &lt;code&gt;(long) (nextDouble() * Long.MAX_VALUE)&lt;/code&gt;<a name="line.172"></a>
<FONT color="green">173</FONT>         * &lt;/pre&gt;&lt;/p&gt;<a name="line.173"></a>
<FONT color="green">174</FONT>         *<a name="line.174"></a>
<FONT color="green">175</FONT>         * @return  the next pseudorandom, uniformly distributed &lt;code&gt;long&lt;/code&gt;<a name="line.175"></a>
<FONT color="green">176</FONT>         *value from this random number generator's sequence<a name="line.176"></a>
<FONT color="green">177</FONT>         */<a name="line.177"></a>
<FONT color="green">178</FONT>        public long nextLong() {<a name="line.178"></a>
<FONT color="green">179</FONT>            return (long) (nextDouble() * Long.MAX_VALUE);<a name="line.179"></a>
<FONT color="green">180</FONT>        }<a name="line.180"></a>
<FONT color="green">181</FONT>    <a name="line.181"></a>
<FONT color="green">182</FONT>        /**<a name="line.182"></a>
<FONT color="green">183</FONT>         * Returns the next pseudorandom, uniformly distributed<a name="line.183"></a>
<FONT color="green">184</FONT>         * &lt;code&gt;boolean&lt;/code&gt; value from this random number generator's<a name="line.184"></a>
<FONT color="green">185</FONT>         * sequence.  <a name="line.185"></a>
<FONT color="green">186</FONT>         * &lt;p&gt;  <a name="line.186"></a>
<FONT color="green">187</FONT>         * The default implementation returns <a name="line.187"></a>
<FONT color="green">188</FONT>         * &lt;pre&gt;<a name="line.188"></a>
<FONT color="green">189</FONT>         * &lt;code&gt;nextDouble() &lt;= 0.5&lt;/code&gt;<a name="line.189"></a>
<FONT color="green">190</FONT>         * &lt;/pre&gt;&lt;/p&gt;<a name="line.190"></a>
<FONT color="green">191</FONT>         * <a name="line.191"></a>
<FONT color="green">192</FONT>         * @return  the next pseudorandom, uniformly distributed<a name="line.192"></a>
<FONT color="green">193</FONT>         * &lt;code&gt;boolean&lt;/code&gt; value from this random number generator's<a name="line.193"></a>
<FONT color="green">194</FONT>         * sequence<a name="line.194"></a>
<FONT color="green">195</FONT>         */<a name="line.195"></a>
<FONT color="green">196</FONT>        public boolean nextBoolean() {<a name="line.196"></a>
<FONT color="green">197</FONT>            return nextDouble() &lt;= 0.5;<a name="line.197"></a>
<FONT color="green">198</FONT>        }<a name="line.198"></a>
<FONT color="green">199</FONT>    <a name="line.199"></a>
<FONT color="green">200</FONT>         /**<a name="line.200"></a>
<FONT color="green">201</FONT>         * Returns the next pseudorandom, uniformly distributed &lt;code&gt;float&lt;/code&gt;<a name="line.201"></a>
<FONT color="green">202</FONT>         * value between &lt;code&gt;0.0&lt;/code&gt; and &lt;code&gt;1.0&lt;/code&gt; from this random<a name="line.202"></a>
<FONT color="green">203</FONT>         * number generator's sequence.  <a name="line.203"></a>
<FONT color="green">204</FONT>         * &lt;p&gt;  <a name="line.204"></a>
<FONT color="green">205</FONT>         * The default implementation returns <a name="line.205"></a>
<FONT color="green">206</FONT>         * &lt;pre&gt;<a name="line.206"></a>
<FONT color="green">207</FONT>         * &lt;code&gt;(float) nextDouble() &lt;/code&gt;<a name="line.207"></a>
<FONT color="green">208</FONT>         * &lt;/pre&gt;&lt;/p&gt;<a name="line.208"></a>
<FONT color="green">209</FONT>         *<a name="line.209"></a>
<FONT color="green">210</FONT>         * @return  the next pseudorandom, uniformly distributed &lt;code&gt;float&lt;/code&gt;<a name="line.210"></a>
<FONT color="green">211</FONT>         * value between &lt;code&gt;0.0&lt;/code&gt; and &lt;code&gt;1.0&lt;/code&gt; from this<a name="line.211"></a>
<FONT color="green">212</FONT>         * random number generator's sequence<a name="line.212"></a>
<FONT color="green">213</FONT>         */<a name="line.213"></a>
<FONT color="green">214</FONT>        public float nextFloat() {<a name="line.214"></a>
<FONT color="green">215</FONT>            return (float) nextDouble();<a name="line.215"></a>
<FONT color="green">216</FONT>        }<a name="line.216"></a>
<FONT color="green">217</FONT>    <a name="line.217"></a>
<FONT color="green">218</FONT>        /**<a name="line.218"></a>
<FONT color="green">219</FONT>         * Returns the next pseudorandom, uniformly distributed <a name="line.219"></a>
<FONT color="green">220</FONT>         * &lt;code&gt;double&lt;/code&gt; value between &lt;code&gt;0.0&lt;/code&gt; and<a name="line.220"></a>
<FONT color="green">221</FONT>         * &lt;code&gt;1.0&lt;/code&gt; from this random number generator's sequence.  <a name="line.221"></a>
<FONT color="green">222</FONT>         * &lt;p&gt;<a name="line.222"></a>
<FONT color="green">223</FONT>         * This method provides the underlying source of random data used by the<a name="line.223"></a>
<FONT color="green">224</FONT>         * other methods.&lt;/p&gt;   <a name="line.224"></a>
<FONT color="green">225</FONT>         *<a name="line.225"></a>
<FONT color="green">226</FONT>         * @return  the next pseudorandom, uniformly distributed <a name="line.226"></a>
<FONT color="green">227</FONT>         *  &lt;code&gt;double&lt;/code&gt; value between &lt;code&gt;0.0&lt;/code&gt; and<a name="line.227"></a>
<FONT color="green">228</FONT>         *  &lt;code&gt;1.0&lt;/code&gt; from this random number generator's sequence<a name="line.228"></a>
<FONT color="green">229</FONT>         */  <a name="line.229"></a>
<FONT color="green">230</FONT>        public abstract double nextDouble();  <a name="line.230"></a>
<FONT color="green">231</FONT>    <a name="line.231"></a>
<FONT color="green">232</FONT>        /**<a name="line.232"></a>
<FONT color="green">233</FONT>         * Returns the next pseudorandom, Gaussian ("normally") distributed<a name="line.233"></a>
<FONT color="green">234</FONT>         * &lt;code&gt;double&lt;/code&gt; value with mean &lt;code&gt;0.0&lt;/code&gt; and standard<a name="line.234"></a>
<FONT color="green">235</FONT>         * deviation &lt;code&gt;1.0&lt;/code&gt; from this random number generator's sequence.<a name="line.235"></a>
<FONT color="green">236</FONT>         * &lt;p&gt;<a name="line.236"></a>
<FONT color="green">237</FONT>         * The default implementation uses the &lt;em&gt;Polar Method&lt;/em&gt;<a name="line.237"></a>
<FONT color="green">238</FONT>         * due to G.E.P. Box, M.E. Muller and G. Marsaglia, as described in <a name="line.238"></a>
<FONT color="green">239</FONT>         * D. Knuth, &lt;u&gt;The Art of Computer Programming&lt;/u&gt;, 3.4.1C.&lt;/p&gt;<a name="line.239"></a>
<FONT color="green">240</FONT>         * &lt;p&gt;<a name="line.240"></a>
<FONT color="green">241</FONT>         * The algorithm generates a pair of independent random values.  One of<a name="line.241"></a>
<FONT color="green">242</FONT>         * these is cached for reuse, so the full algorithm is not executed on each<a name="line.242"></a>
<FONT color="green">243</FONT>         * activation.  Implementations that do not override this method should<a name="line.243"></a>
<FONT color="green">244</FONT>         * make sure to call {@link #clear} to clear the cached value in the <a name="line.244"></a>
<FONT color="green">245</FONT>         * implementation of {@link #setSeed(long)}.&lt;/p&gt;<a name="line.245"></a>
<FONT color="green">246</FONT>         * <a name="line.246"></a>
<FONT color="green">247</FONT>         * @return  the next pseudorandom, Gaussian ("normally") distributed<a name="line.247"></a>
<FONT color="green">248</FONT>         * &lt;code&gt;double&lt;/code&gt; value with mean &lt;code&gt;0.0&lt;/code&gt; and<a name="line.248"></a>
<FONT color="green">249</FONT>         * standard deviation &lt;code&gt;1.0&lt;/code&gt; from this random number<a name="line.249"></a>
<FONT color="green">250</FONT>         *  generator's sequence<a name="line.250"></a>
<FONT color="green">251</FONT>         */<a name="line.251"></a>
<FONT color="green">252</FONT>        public double nextGaussian() {<a name="line.252"></a>
<FONT color="green">253</FONT>            if (!Double.isNaN(cachedNormalDeviate)) {<a name="line.253"></a>
<FONT color="green">254</FONT>                double dev = cachedNormalDeviate;<a name="line.254"></a>
<FONT color="green">255</FONT>                cachedNormalDeviate = Double.NaN;<a name="line.255"></a>
<FONT color="green">256</FONT>                return dev;<a name="line.256"></a>
<FONT color="green">257</FONT>            }<a name="line.257"></a>
<FONT color="green">258</FONT>            double v1 = 0;<a name="line.258"></a>
<FONT color="green">259</FONT>            double v2 = 0;<a name="line.259"></a>
<FONT color="green">260</FONT>            double s = 1;<a name="line.260"></a>
<FONT color="green">261</FONT>            while (s &gt;=1 ) { <a name="line.261"></a>
<FONT color="green">262</FONT>                v1 = 2 * nextDouble() - 1; <a name="line.262"></a>
<FONT color="green">263</FONT>                v2 = 2 * nextDouble() - 1; <a name="line.263"></a>
<FONT color="green">264</FONT>                s = v1 * v1 + v2 * v2;<a name="line.264"></a>
<FONT color="green">265</FONT>            }<a name="line.265"></a>
<FONT color="green">266</FONT>            if (s != 0) {<a name="line.266"></a>
<FONT color="green">267</FONT>                s = Math.sqrt(-2 * Math.log(s) / s);   <a name="line.267"></a>
<FONT color="green">268</FONT>            }<a name="line.268"></a>
<FONT color="green">269</FONT>            cachedNormalDeviate = v2 * s;<a name="line.269"></a>
<FONT color="green">270</FONT>            return v1 * s;      <a name="line.270"></a>
<FONT color="green">271</FONT>        }<a name="line.271"></a>
<FONT color="green">272</FONT>    }<a name="line.272"></a>




























































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